Oliver Burkeman on why everything takes longer than you think

Hofstadter's law, conceived by the cognitive scientist Douglas Hofstadter, goes like this: any task you're planning to complete will always take longer than expected - even when Hofstadter's law is taken into account. Even if you know a project will overrun, and build that knowledge into your planning, it'll simply overrun your new estimated finish time, too, Hofstadter says. We chronically underestimate the time things take: that's why Sydney Opera House opened 10 years later than scheduled, and why the new Wembley stadium opened last year, not in 2003, 2005 or 2006, each of which had been, at various points, the predicted completion date. It's also why the list-makers among us get up each day and make to-do lists that by the same evening will seem laughable, even insane.

This is the "planning fallacy", and it's been well-documented by psychologists. (Presumably their experiments took much longer than intended.) It's a strange kind of delusion, since we're not really deluded. We know everything always takes longer than expected; we just seem to forget, again and again. In one study, students were asked when they expected to complete an essay, and gave an average answer of 10 days before deadline. The reality was an average of one day before deadline. Yet when the students were asked when they normally completed such essays, they knew the truth: one day before deadline.

It would be good to find a way around the planning fallacy, since never finishing your to-do list is a joyless way to live, and underestimating task-times means constantly rushing to finish things. (I speak as an expert.) How, though? Intuitively, it feels sensible to work out in detail what your projects involve, to break them into chunks and estimate how long each part will take. But the problem with unforeseen delays is you can't foresee them, no matter how finely detailed your planning. And so, writes Eliezer Yudkowsky on the Oxford University blog OvercomingBias.com, the unlikely trick is to plan in less detail: avoid considering the specifics and simply ask yourself how long it's taken to do roughly similar things before. "You'll get back an answer that sounds hideously long, and clearly reflects no understanding of the special reasons why this task will take less time," he writes. "This answer is true. Deal with it."

Better yet, where possible, avoid planning altogether. Use the "ready, fire, aim" approach, and correct course as you go along. As the blogger Steve Pavlina points out, the advantage is you quickly start getting real feedback. If you're starting a new business, say, you won't have to imagine how customers might respond to your adverts; you'll know. This approach also helps when it comes to those curious tasks that don't obey Hofstadter's law: the ones you fret about for weeks, but that end up taking 10 minutes. Sometimes, the secret to getting things done is just to do them.